The invention relates to an electronic control system for controlling the rotational speed of at least one drive motor of a motor vehicle.
The engine speed in motor vehicles is controlled according to the prior art by taking into account the rotational speed difference between a target rotational speed and a measured actual rotational speed. The rotational speed control function is usually integrated in the engine controller, wherein both the rotational speed difference and the gradient of the actual rotational speed are evaluated for determining the control parameters. A gradient evaluation can provide a faster response to a drifting actual speed than in a exclusive differential speed evaluation, since the controller can take into account the rate of change of the actual speed value. However, such a control system presupposes that the target speed remains at least virtually constant and at least does not exhibit rotational speed jumps.
For electric vehicles and hybrid vehicles with an internal combustion engine and an electric motor as drive motors, the target rotational speed is in many cases no longer approximately constant, but can exhibit significant rotational speed jumps depending on the operating mode of the motor vehicle. For different operating conditions, such hybrid driving, hybrid stopped, electrically driving, electrically stopped, additional starting of a second drive motor, mutually different as well as dynamic target rotational speeds arise, wherein switching between them is possible within a short time. A target rotational speed may also move away from a constant actual speed, which when only considering the rotational speed gradient of the actual rotational speed, does not provide a faster reaction time compared to an evaluation of exclusively the difference in the rotational speed. In these conventional control systems, the gradient evaluation can in special cases even cause an erroneous influence on the rotational speed control.
DE 10 2006 005 468 A1 discloses a method for operating a parallel hybrid drive train of a motor vehicle, wherein the rotational speed of a combustion engine and of an electric motor is controlled for controlling the transmission. This known method, however, does not relate to the rotational speed control of a drive motor of a motor vehicle while taking into account highly variable or abruptly changing target rotational speeds.